Instituto de Química de São Carlos, Universidade de São Paulo, CP 369, São Carlos 13660-970, SP, Brazil.
Department of Microbiology, Institute of Biomedical Science, Universidade Tecnológica Federal do Paraná, Rua Deputado Heitor de Alencar Furtado, Curitiba 81280-340, PR, Brazil.
Molecules. 2022 Jul 11;27(14):4434. doi: 10.3390/molecules27144434.
Low Field Time-Domain Nuclear Magnetic Resonance (TD-NMR) relaxometry was used to determine moisture, fat, and defatted dry matter contents in "requeijão cremoso" (RC) processed cheese directly in commercial packaged (plastic cups or tubes with approximately 200 g). Forty-five samples of commercial RC types (traditional, light, lactose-free, vegan, and fiber) were analyzed using longitudinal (T) and transverse (T) relaxation measurements in a wide bore Halbach magnet (0.23 T) with a 100 mm probe. The T and T analyses were performed using CWFP-T (Continuous Wave Free Precession) and CPMG (Carr-Purcell-Meiboom-Gill) single shot pulses. The scores of the principal component analysis (PCA) of CWFP-T and CPMG signals did not show clustering related to the RC types. Optimization by variable selection was carried out with ordered predictors selection (OPS), providing simpler and predictive partial least squares (PLS) calibration models. The best results were obtained with CWFP-T data, with root-mean-square errors of prediction (RMSEP) of 1.38, 4.71, 3.28, and 3.00% for defatted dry mass, fat in the dry and wet matter, and moisture, respectively. Therefore, CWFP-T data modeled with chemometrics can be a fast method to monitor the quality of RC directly in commercial packages.
低场时域核磁共振（TD-NMR）弛豫谱法用于直接在商业包装（约 200 克的塑料杯或管）中测定“requeijão cremoso”（RC）加工奶酪中的水分、脂肪和脱脂干物质含量。使用宽孔径 Halbach 磁铁（0.23 T）和 100mm 探头对 45 种商业 RC 类型（传统型、低脂型、无乳糖型、素食型和纤维型）进行了纵向（T1）和横向（T2）弛豫测量，采用连续波自由进动（CWFP-T）和 CPMG（ Carr-Purcell-Meiboom-Gill）单次脉冲进行 T1 和 T2 分析。CWFP-T 和 CPMG 信号的主成分分析（PCA）得分并未显示与 RC 类型相关的聚类。通过变量选择进行优化，采用有序预测因子选择（OPS），提供更简单和预测性的偏最小二乘（PLS）校准模型。CWFP-T 数据的结果最佳，其脱脂干物质、干物质和湿物质中的脂肪以及水分的预测均方根误差（RMSEP）分别为 1.38%、4.71%、3.28%和 3.00%。因此，通过化学计量学建模的 CWFP-T 数据可以成为一种快速方法，直接在商业包装中监测 RC 的质量。
